scholarly journals Mutations in Salmonella Pathogenicity Island 2 (SPI2) Genes Affecting Transcription of SPI1 Genes and Resistance to Antimicrobial Agents

1998 ◽  
Vol 180 (18) ◽  
pp. 4775-4780 ◽  
Author(s):  
Jörg Deiwick ◽  
Thomas Nikolaus ◽  
Jaqueline E. Shea ◽  
Colin Gleeson ◽  
David W. Holden ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Antimicrobial Agents ◽  
Type Iii Secretion System ◽  
Polymyxin B ◽  
Secretion System ◽  
Effector Proteins ◽  
Secretion Systems ◽  
Type Iii ◽  
Genes Encoding

ABSTRACT The Salmonella typhimurium genome contains two pathogenicity islands (SPI) with genes encoding type III secretion systems for virulence proteins. SPI1 is required for the penetration of the epithelial layer of the intestine. SPI2 is important for the subsequent proliferation of bacteria in the spleens of infected hosts. Although most mutations in SPI2 lead to a strong reduction of virulence, they have different effects in vitro, with some mutants having significantly increased sensitivity to gentamicin and the antibacterial peptide polymyxin B. Previously we showed that certain mutations in SPI2 affect the ability of S. typhimurium to secrete SPI1 effector proteins and to invade cultured eukaryotic cells. In this study, we show that these SPI2 mutations affect the expression of the SPI1 invasion genes. Analysis of reporter fusions to various SPI1 genes reveals highly reduced expression of sipC,prgK, and hilA, the transcriptional activator of SPI1 genes. These observations indicate that the expression of one type III secretion system can be influenced dramatically by mutations in genes encoding a second type III secretion system in the same cell.

scholarly journals CesD2 of Enteropathogenic Escherichia coli Is a Second Chaperone for the Type III Secretion Translocator Protein EspD

2003 ◽  
Vol 71 (4) ◽  
pp. 2130-2141 ◽  
Author(s):  
Bianca C. Neves ◽  
Rosanna Mundy ◽  
Liljana Petrovska ◽  
Gordon Dougan ◽  
Stuart Knutton ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Translocator Protein ◽  
Type Iii ◽  
Genes Encoding

ABSTRACT Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli are extracellular pathogens that employ a type III secretion system to export translocator and effector proteins, proteins which facilitates colonization of the mucosal surface of the intestine via formation of attaching and effacing (A/E) lesions. The genes encoding the proteins for A/E lesion formation are located on a pathogenicity island, termed the locus of enterocyte effacement (LEE), which contains eae encoding intimin as well as the type III secretion system and effector genes. Many type III secreted proteins are stabilized and maintained in a secretion-competent conformation in the bacterial cytosol by specific chaperone proteins. Three type III chaperones have been described thus far within the EPEC LEE region: CesD, for the translocator proteins EspB and EspD; CesT, for the effector proteins Tir and Map; and CesF, for EspF. In this study we report the characterization of CesD2 (previously Orf27), a second LEE-encoded chaperone for EspD. We show specific CesD2-EspD protein interaction which appears to be necessary for proper EspD secretion in vitro and pathogenesis in vivo as demonstrated in the A/E-lesion-forming mouse pathogen Citrobacter rodentium.

scholarly journals Chlamydial Type III Secretion System Is Encoded on Ten Operons Preceded by Sigma 70-Like Promoter Elements

2006 ◽  
Vol 189 (1) ◽  
pp. 198-206 ◽  
Author(s):  
P. Scott Hefty ◽  
Richard S. Stephens
Keyword(s):  
Type Iii Secretion ◽  
Transcriptional Start Site ◽  
Type Iii Secretion System ◽  
Regulatory Elements ◽  
Secretion System ◽  
Secretion Systems ◽  
Promoter Elements ◽  
Type Iii ◽  
Type Iii Secretion Systems ◽  
Genes Encoding

ABSTRACT Many gram-negative bacterial pathogens employ type III secretion systems for infectious processes. Chlamydiae are obligate intracellular bacteria that encode a conserved type III secretion system that is likely requisite for growth. Typically, genes encoding type III secretion systems are located in a single locus; however, for chlamydiae these genes are scattered throughout the genome. Little is known regarding the gene regulatory mechanisms for this essential virulence determinant. To facilitate identification of cis-acting transcriptional regulatory elements, the operon structure was determined. This analysis revealed 10 operons that contained 37 genes associated with the type III secretion system. Linkage within these operons suggests a role in type III secretion for each of these genes, including 13 genes encoding proteins with unknown function. The transcriptional start site for each operon was determined. In conjunction with promoter activity assays, this analysis revealed that the type III secretion system operons encode σ70-like promoter elements. Transcriptional initiation by a sigma factor responsible for constitutive gene expression indicates that undefined activators or repressors regulate developmental stage-specific expression of chlamydial type III secretion system genes.

scholarly journals Expression of and secretion through the Aeromonas salmonicida type III secretion system

Microbiology ◽  
2006 ◽  
Vol 152 (5) ◽  
pp. 1275-1286 ◽  
Author(s):  
Roger O. Ebanks ◽  
Leah C. Knickle ◽  
Michel Goguen ◽  
Jessica M. Boyd ◽  
Devanand M. Pinto ◽  
...  
Keyword(s):  
Growth Temperature ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Growth Conditions ◽  
Secretion System ◽  
Aeromonas Salmonicida ◽  
Effector Proteins ◽  
Type Iii ◽  
Low Calcium

Aeromonas salmonicida subsp. salmonicida is the aetiological agent of furunculosis, a disease of farmed and wild salmonids. The type III secretion system (TTSS) is one of the primary virulence factors in A. salmonicida. Using a combination of differential proteomic analysis and reverse transcriptase (RT)-PCR, it is shown that A. salmonicida A449 induces the expression of TTSS proteins at 28 °C, but not at its more natural growth temperature of 17 °C. More modest increases in expression occur at 24 °C. This temperature-induced up-regulation of the TTSS in A. salmonicida A449 occurs within 30 min of a growth temperature increase from 16 to 28 °C. Growth conditions such as low-iron, low pH, low calcium, growth within the peritoneal cavity of salmon and growth to high cell densities do not induce the expression of the TTSS in A. salmonicida A449. The only other known growth condition that induces expression of the TTSS is growth of the bacterium at 16 °C in salt concentrations ranging from 0·19 to 0·38 M NaCl. It is also shown that growth at 28 °C followed by exposure to low calcium results in the secretion of one of the TTSS effector proteins. This study presents a simple in vitro model for the expression of TTSS proteins in A. salmonicida.

scholarly journals A Novel Periplasmic Protein, VrpA, Contributes to Efficient Protein Secretion by the Type III Secretion System in Xanthomonas spp.

2015 ◽  
Vol 28 (2) ◽  
pp. 143-153 ◽  
Author(s):  
Xiaofeng Zhou ◽  
Xiufang Hu ◽  
Jinyun Li ◽  
Nian Wang
Keyword(s):  
Protein Secretion ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Periplasmic Protein ◽  
Transcription Activator ◽  
Type Iii Effector ◽  
Type Iii

Efficient secretion of type III effector proteins from the bacterial cytoplasm to host cell cytosol via a type III secretion system (T3SS) is crucial for virulence of plant-pathogenic bacterium. Our previous study revealed a conserved hypothetical protein, virulence-related periplasm protein A (VrpA), which was identified as a critical virulence factor for Xanthomonas citri subsp. citri. In this study, we demonstrate that mutation of vrpA compromises X. citri subsp. citri virulence and hypersensitive response induction. This deficiency is also observed in the X. campestris pv. campestris strain, suggesting a functional conservation of VrpA in Xanthomonas spp. Our study indicates that VrpA is required for efficient protein secretion via T3SS, which is supported by multiple lines of evidence. A CyaA reporter assay shows that VrpA is involved in type III effector secretion; quantitative reverse-transcription polymerase chain reaction analysis suggests that the vrpA mutant fails to activate citrus-canker-susceptible gene CsLOB1, which is transcriptionally activated by transcription activator-like effector PthA4; in vitro secretion study reveals that VrpA plays an important role in secretion of T3SS pilus, translocon, and effector proteins. Our data also indicate that VrpA in X. citri subsp. citri localizes to bacterial periplasmic space and the periplasmic localization is required for full function of VrpA and X. citri subsp. citri virulence. Protein–protein interaction studies show that VrpA physically interacts with periplasmic T3SS components HrcJ and HrcC. However, the mutation of VrpA does not affect T3SS gene expression. Additionally, VrpA is involved in X. citri subsp. citri tolerance of oxidative stress. Our data contribute to the mechanical understanding of an important periplasmic protein VrpA in Xanthomonas spp.

scholarly journals Closing the Circle on the Discovery of Genes Encoding Hrp Regulon Members and Type III Secretion System Effectors in the Genomes of Three Model Pseudomonas syringae Strains

2006 ◽  
Vol 19 (11) ◽  
pp. 1151-1158 ◽  
Author(s):  
Magdalen Lindeberg ◽  
Samuel Cartinhour ◽  
Christopher R. Myers ◽  
Lisa M. Schechter ◽  
David J. Schneider ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Active Member ◽  
Tomato Dc3000 ◽  
Type Iii ◽  
Effector Genes ◽  
Genes Encoding

Pseudomonas syringae strains translocate large and distinct collections of effector proteins into plant cells via the type III secretion system (T3SS). Mutations in T3SS-encoding hrp genes are unable to elicit the hypersensitive response or pathogenesis in nonhost and host plants, respectively. Mutations in individual effectors lack strong phenotypes, which has impeded their discovery. P. syringae effectors are designated Hop (Hrp outer protein) or Avr (avirulence) proteins. Some Hop proteins are considered to be extracellular T3SS helpers acting at the plant-bacterium interface. Identification of complete sets of effectors and related proteins has been enabled by the application of bioinformatic and high-throughput experimental techniques to the complete genome sequences of three model strains: P. syringae pv. tomato DC3000, P. syringae pv. phaseolicola 1448A, and P. syringae pv. syringae B728a. Several recent papers, including three in this issue of Molecular Plant-Microbe Interactions, address the effector inventories of these strains. These studies establish that active effector genes in P. syringae are expressed by the HrpL alternative sigma factor and can be predicted on the basis of cis Hrp promoter sequences and N-terminal amino-acid patterns. Among the three strains analyzed, P. syringae pv. tomato DC3000 has the largest effector inventory and P. syringae pv. syringae B728a has the smallest. Each strain has several effector genes that appear inactive. Only five of the 46 effector families that are represented in these three strains have an active member in all of the strains. Web-based community resources for managing and sharing growing information on these complex effector arsenals should help future efforts to understand how effectors promote P. syringae virulence.

scholarly journals SOS Regulation of the Type III Secretion System of Enteropathogenic Escherichia coli

2007 ◽  
Vol 189 (7) ◽  
pp. 2863-2872 ◽  
Author(s):  
Jay L. Mellies ◽  
Kenneth R. Haack ◽  
Derek C. Galligan
Keyword(s):  
Escherichia Coli ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Watery Diarrhea ◽  
Type Iii ◽  
Lexa Protein

ABSTRACT Genomes of bacterial pathogens contain and coordinately regulate virulence-associated genes in order to cause disease. Enteropathogenic Escherichia coli (EPEC), a major cause of watery diarrhea in infants and a model gram-negative pathogen, expresses a type III secretion system (TTSS) that is encoded by the locus of enterocyte effacement (LEE) and is necessary for causing attaching and effacing intestinal lesions. Effector proteins encoded by the LEE and in cryptic prophage are injected into the host cell cytoplasm by the TTTS apparatus, ultimately leading to diarrhea. The LEE is comprised of multiple polycistronic operons, most of which are controlled by the global, positive regulator Ler. Here we demonstrated that the LEE2 and LEE3 operons also responded to SOS signaling and that this regulation was LexA dependent. As determined by a DNase I protection assay, purified LexA protein bound in vitro to a predicted SOS box located in the divergent, overlapping LEE2/LEE3 promoters. Expression of the lexA1 allele, encoding an uncleavable LexA protein in EPEC, resulted in reduced secretion, particularly in the absence of the Ler regulator. Finally, we obtained evidence that the cryptic phage-located nleA gene encoding an effector molecule is SOS regulated. Thus, we demonstrated, for the first time to our knowledge, that genes encoding components of a TTSS are regulated by the SOS response, and our data might explain how a subset of EPEC effector proteins, encoded in cryptic prophages, are coordinately regulated with the LEE-encoded TTSS necessary for their translocation into host cells.

scholarly journals Bioinformatics-Enabled Identification of the HrpL Regulon and Type III Secretion System Effector Proteins of Pseudomonas syringae pv. phaseolicola 1448A

2006 ◽  
Vol 19 (11) ◽  
pp. 1193-1206 ◽  
Author(s):  
Monica Vencato ◽  
Fang Tian ◽  
James R. Alfano ◽  
C. Robin Buell ◽  
Samuel Cartinhour ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Candidate Gene Approach ◽  
Type Iii Effectors ◽  
Type Iii ◽  
Genes Encoding

The ability of Pseudomonas syringae pv. phaseolicola to cause halo blight of bean is dependent on its ability to translocate effector proteins into host cells via the hypersensitive response and pathogenicity (Hrp) type III secretion system (T3SS). To identify genes encoding type III effectors and other potential virulence factors that are regulated by the HrpL alternative sigma factor, we used a hidden Markov model, weight matrix model, and type III targeting-associated patterns to search the genome of P. syringae pv. phaseolicola 1448A, which recently was sequenced to completion. We identified 44 high-probability putative Hrp promoters upstream of genes encoding the core T3SS machinery, 27 candidate effectors and related T3SS substrates, and 10 factors unrelated to the Hrp system. The expression of 13 of these candidate HrpL regulon genes was analyzed by real-time polymerase chain reaction, and all were found to be upregulated by HrpL. Six of the candidate type III effectors were assayed for T3SS-dependent translocation into plant cells using the Bordetella pertussis calmodulin-dependent adenylate cyclase (Cya) translocation reporter, and all were translocated. PSPPH1855 (ApbE-family protein) and PSPPH3759 (alcohol dehydrogenase) have no apparent T3SS-related function; however, they do have homologs in the model strain P. syringae pv. tomato DC3000 (PSPTO2105 and PSPTO0834, respectively) that are similarly upregulated by HrpL. Mutations were constructed in the DC3000 homologs and found to reduce bacterial growth in host Arabidopsis leaves. These results establish the utility of the bioinformatic or candidate gene approach to identifying effectors and other genes relevant to pathogenesis in P. syringae genomes.

scholarly journals The Vibrio cholerae trh Gene Is Coordinately RegulatedIn Vitrowith Type III Secretion System Genes by VttRA/VttRBbut Does Not Contribute to Caco2-BBE Cell Cytotoxicity

2012 ◽  
Vol 80 (12) ◽  
pp. 4444-4455 ◽  
Author(s):  
Kelly A. Miller ◽  
Elaine Hamilton ◽  
Michelle Dziejman
Keyword(s):  
Vibrio Cholerae ◽  
Type Iii Secretion ◽  
Genomic Island ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Dependent Manner ◽  
Content Type ◽  
Type Iii ◽  
Genes Encoding

ABSTRACTNumerous virulence factors have been associated with pathogenic non-O1/non-O139 serogroup strains ofVibrio cholerae. Among them are thethermostabledirecthemolysin (TDH) and theTDH-relatedhemolysin (TRH), which share amino acid similarities to the TDH and TRH proteins ofVibrio parahaemolyticus, where they have been shown to contribute to pathogenesis. Although TDH and TRH homologs can be encoded on extrachromosomal elements inV. cholerae, type III secretion system (T3SS)-positive strains, such as AM-19226, carry a copy oftrhwithin the T3SS genomic island. Transcriptional fusion analysis showed that in strain AM-19226,trhexpression is regulated in a bile-dependent manner by a family of transmembrane transcriptional regulators that includes VttRA, VttRB, and ToxR. Genes encoding T3SS structural components are expressed under similar conditions, suggesting that within the T3SS genomic island, genes encoding proteins unrelated to the T3SS and loci involved in T3SS synthesis are coregulated. Despite similarin vitroexpression patterns, however, TRH is not required for AM-19226 to colonize the infant mouse intestine, nor does it contribute to bile-mediated cytotoxicity when strain AM-19226 is cocultured with the mammalian cell line Caco2-BBE. Instead, we found that a functional T3SS is essential for AM-19226 to induce bile-mediated cytotoxicityin vitro. Collectively, the results are consistent with a more minor role for theV. choleraeTRH in T3SS-positive strains compared to the functions attributed to theV. parahaemolyticusTDH and TRH proteins.

scholarly journals Evidence for a Type III Secretion System in Aeromonas salmonicida subsp. salmonicida

2002 ◽  
Vol 184 (21) ◽  
pp. 5966-5970 ◽  
Author(s):  
Sarah E. Burr ◽  
Katja Stuber ◽  
Thomas Wahli ◽  
Joachim Frey
Keyword(s):  
Type Iii Secretion ◽  
Type Strain ◽  
Wild Type Strain ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Aeromonas Salmonicida ◽  
Broad Host Range ◽  
Wild Type ◽  
Secretion Systems ◽  
Type Iii

ABSTRACT Aeromonas salmonicida subsp. salmonicida, the etiological agent of furunculosis, is an important fish pathogen. We have screened this bacterium with a broad-host-range probe directed against yscV, the gene that encodes the archetype of a highly conserved family of inner membrane proteins found in every known type III secretion system. This has led to the identification of seven open reading frames that encode homologues to proteins functioning within the type III secretion systems of Yersinia species. Six of these proteins are encoded by genes comprising a virA operon. The A. salmonicida subsp. salmonicida yscV homologue, ascV, was inactivated by marker replacement mutagenesis and used to generate an isogenic ascV mutant. Comparison of the extracellular protein profiles from the ascV mutant and the wild-type strain indicates that A. salmonicida subsp. salmonicida secretes proteins via a type III secretion system. The recently identified ADP-ribosylating toxin AexT was identified as one such protein. Finally, we have compared the toxicities of the wild-type A. salmonicida subsp. salmonicida strain and the ascV mutant against RTG-2 rainbow trout gonad cells. While infection with the wild-type strain results in significant morphological changes, including cell rounding, infection with the ascV mutant has no toxic effect, indicating that the type III secretion system we have identified plays an important role in the virulence of this pathogen.

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